1. Technical Field
The present invention relates to a gas generator for a vehicle occupant restraint, such as an air bag, and to the gas generating material used in the gas generator.
2. Description of the Prior Art
A large number of gas generating materials have been proposed for generating gas to operate a vehicle occupant restraint such as an air bag or a pretensioner for a seat belt. For air bags, in particular, materials which produce an inert gas, such as a nitrogen, have been preferred.
There are practical constraints, however, which limit the effectiveness of many nitrogen gas generating materials which have been proposed. The products of reaction other than nitrogen gas, which are produced during combustion of the gas generating materials, should be non-toxic, present in non-toxic amounts or capable of being kept out of or removed from the nitrogen gas. The gas generating material should also be capable of a near instantaneous production of gas, without explosive force or too high a temperature. The gas generating material also has to be safe to handle, and non-combustible, under normal circumstances, except when purposely ignited.
The nitrogen gas generating materials which are currently used contain a metal or an alkali metal component, such as a metal oxidant and/or metal azide. These compounds, on combustion, produce molten or solid reaction products which have to be filtered from the nitrogen gas. Filters for this purpose are expensive, as well as heavy, and add considerably to the cost and weight of the vehicle occupant restraint assembly.